US20130002373A1 - High rejection band-stop filter and diplexer using such filters - Google Patents

High rejection band-stop filter and diplexer using such filters Download PDF

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Publication number
US20130002373A1
US20130002373A1 US13/529,627 US201213529627A US2013002373A1 US 20130002373 A1 US20130002373 A1 US 20130002373A1 US 201213529627 A US201213529627 A US 201213529627A US 2013002373 A1 US2013002373 A1 US 2013002373A1
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Prior art keywords
resonators
filter
series
substrate
filters
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US13/529,627
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English (en)
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Jean-Luc Robert
Dominique Lo Hine Tong
Ali Louzir
Philippe Minard
Jean-Yves Le Naour
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Assigned to THOMSON LICENSING reassignment THOMSON LICENSING ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LOUZIR, ALI, LE NAOUR, JEAN-YVES, LO HINE TONG, DOMINIQUE, MINARD, PHILIPPE, ROBERT, JEAN-LUC
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters
    • H01P1/20327—Electromagnetic interstage coupling
    • H01P1/20336—Comb or interdigital filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/213—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/213—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies
    • H01P1/2135—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies using strip line filters

Definitions

  • the present invention relates to a high rejection band-stop filter, more specifically it relates to a band-stop filter in printed technology.
  • the present invention also relates to diplexers using such filters.
  • the 2.4 GHz frequency band is assigned to the transfer of standard data or video while the 5 GHz frequency band is assigned to the transfer of high-definition streams or high resolution games.
  • the 2.4 GHz WiFi band only has three adjacent channels while the 5 GHz WiFi band has 24 channels.
  • a WiFi access point ensuring concurrent functioning in two contiguous 5 GHz frequency bands enables the distribution of contents in future domestic networks to be noticeably improved and limits potential interference problems.
  • the challenge consisting in sharing a single system of antennas with two concurrent radio circuits in the same frequency band, namely the 5 GHz frequency band, resides in the isolation capacity between two active circuits, this challenge being all the more significant as the two frequency bands are practically contiguous.
  • a conventional stub in open circuit namely a transmission line 1 with an input terminal referenced as “input” and an output terminal referenced as “output”, a stub 2 of length ⁇ /4 where ⁇ corresponds to the operating frequency, the transmission line having a width Wc while the stub has a weaker width, Ws,
  • a “SPUR-LINE” pattern as shown in FIG. 1 , a transmission stub 3 comprising an input point “Input” and an output point “Output”, this line being fitted with a slot 4 cutting a stub 3 a of length ⁇ /4, the slot having a width G, the stub 3 a a width Ws and the transmission line 3 ′ a width Wc,
  • resonators can be symbolised by the elements R 1 and the coupling line by the element Phi representing the coupling phase between resonators.
  • a band-stop filter is shown formed of two resonators in series head to tail.
  • a substrate 20 equipped with a conductive layer was produced a first resonator 21 a interconnected via a coupling line 22 to a second resonator 21 b mounted head to tail with respect to the resonator 21 a .
  • the two embodiments of FIGS. 2 and 3 were simulated providing, for the coupling line 12 or 22 , different lengths that enable the inter-resonator coupling phase to be modified.
  • the present invention proposes a new stop band filter structure using resonators constituted of stubs in open circuit inserted in a transmission line, specifically a microstrip line, that has both a significant rejection in the operating frequency band, namely 5 GHz in a particular embodiment, and that is also compact.
  • the purpose of the present invention is thus an asymmetrical response stop band filter comprising, a substrate with a ground plane, an etched transmission line extending between an input terminal and an output terminal and at least two resonators, each resonator being constituted by a section of printed line or “stub” in open circuit, embedded into the printed transmission line, characterized in that the at least two resonators are positioned in parallel together, on the substrate and interconnected in series in the same direction or head to tail.
  • the parallel position of the resonators enables a compact filter to be obtained. Contrary to standard microstrip type topologies, this structure has a co-planar propagation mode and as a result, no coupling appears between the various resonators, the field remaining concentrated between the stub and the associated slots.
  • the number of resonators constituting the filter is calculated according to the level of rejection required. Moreover, the length of the transmission line interconnecting two resonators, corresponds to a coupling length less than 20° at the frequency considered for a connection in series in the same direction and at 90° for a connection in series head to tail.
  • the substrate is a low loss substrate such as the substrate known as Arlon 25N.
  • the substrate used can also be a standard hyper-frequency substrate such as the substrate called RO4003 by Rogers.
  • the present invention also relates to a diplexer enabling operation in the adjacent frequency bands, characterized in that it comprises two asymmetrical response stop band filters as described above, the two filters being interconnected via an interconnection line ensuring their reciprocal isolation, one of the filters operating in the high band and the other filter operating in the low band of the band of operating frequencies.
  • the filter operating in the high band comprises resonators interconnected in series head to tail and the filter operating in the low band comprises resonators interconnected in series in the same direction.
  • FIG. 1 already described diagrammatically represents different embodiments of resonators as well as their transmission and reflection curves, according to the frequency.
  • FIG. 2 shows a first embodiment of a stop band filter comprising two open circuit “stub” type resonators, mounted in series in direct direction as well as the transmission curves for different lengths of the coupling line providing the phase.
  • FIG. 3 shows another embodiment of a stop band filter formed of two open circuit “stub” type resonators, mounted in series head to tail as well as the transmission curves for different lengths of the coupling line between the two resonators.
  • FIG. 4 shows a first embodiment of a high rejection stop band filter in accordance with the present invention as well as the reflection and transmission curves of said filter.
  • FIG. 5 shows a second embodiment of a high rejection stop band filter in accordance with the present invention as well as the reflection and transmission curves of said filter.
  • FIG. 6 shows, for the embodiment of FIG. 5 , the reflection and transmission curves according to the number of resonators constituting the stop band filter.
  • FIG. 7 shows an embodiment of a diplexer constituted by two stop band filters according to the embodiments of FIG. 4 and FIG. 5 as well as their reflection and transmission curves.
  • FIG. 8 shows the measured responses of a particular embodiment of stop band filters in (a) and of the diplexer in (b).
  • FIG. 4 a first embodiment is shown of a high rejection stop band filter in accordance with the present invention.
  • the left side of FIG. 4 diagrammatically shows the structure of the filter while the right side of FIG. 4 provides the transmission and reflection curves simulated for said filter.
  • each resonator 31 a, 31 b, 31 c and 31 d was realised mounted in parallel together in cascade.
  • Each resonator 31 a, 31 b, 31 c and 31 d is formed by a stub of length ⁇ /4 etched in a transmission line, as described for the embodiment C of FIG. 1 .
  • the resonator 31 a is connected to the resonator 31 b in series in the same direction by a coupling stub 32 a whose length determines the coupling phase.
  • the resonator 31 b is connected to the resonator 31 c in series in the same direction, by a coupling line 32 b and the resonator 31 c is connected to the resonator 31 d by a coupling line 32 c.
  • the length of the coupling line 32 a, 32 b, 32 c is selected to be as low as possible, which enables the steepness of the filter to be accentuated at the transition of two WiFi bands, as explained with reference to FIG. 2 .
  • the filter input is realised at the level of port 1 and the output of the filter is realised at the level of port 2 .
  • the electromagnetic simulation of the filter of FIG. 4 is shown on the right side of FIG. 4 .
  • the filter of FIG. 4 is particularly adapted to operate in the low band, namely in the embodiment shown, the frequencies band comprised between 5.15-5.35 GHz. It has a more steep edge on the right side of the transmission curve. Thus, this filter type will be used rather as a low band filter.
  • FIG. 5 A description will now be given, with reference to FIG. 5 , of another embodiment of a high rejection stop band filter in accordance with the present invention.
  • the left side diagrammatically shows the filter structure while the right side shows the simulated transmission and reflection curves of said filter.
  • resonators 41 a, 41 b, 41 c and 41 d were realised in cascade on a substrate 40 with a conductive layer.
  • the four resonators are mounted in series head to tail.
  • Each resonator 41 a, 41 b, 41 c, 41 d is formed, likewise the embodiment of FIG. 4 , of a stub of length ⁇ /4 etched in a transmission line.
  • two resonators 41 a , 41 b are interconnected head to tail via a coupling line 42 a for which the length determines the coupling phase.
  • the resonator 41 b is interconnected to the resonator 41 c via a coupling line 42 b and the resonator 41 c is interconnected to the resonator 41 d via a coupling line 42 c.
  • the filter input is realised at the level of the port 1 and the filter output is realised at the level of the port 2 .
  • the simulations carried out on the filter of FIG. 5 provide the reflection and transmission curves shown in the right side of FIG. 5 . In this case, an abrupt edge is observed on the left side of transmission curves and transmission zeros between 5.470 and 5.720 GHz.
  • This filter structure is used mainly as a stop band filter for the high band of the 5 GHz frequency band.
  • a stop band filter was simulated comprising six resonators mounted head to tail while on the right side, transmission and reflection curves are shown of stop band filters with four resonators mounted head to tail as in FIG. 5 .
  • the curves obtained show that a greater rejection level is obtained with a stop band filter comprising six resonators mounted in series head to tail.
  • the diplexer is constituted on a substrate 50 with a conductive layer, of a first filter 51 formed of six resonators in series head to tail enabling a high band filter to be obtained.
  • This resonator 51 is connected via a microstrip line 53 to a band-stop filter 52 formed of four resonators in series in direct direction providing a low band filter, the microstrip line interconnecting the resonators 51 and 52 enabling a reciprocal isolation to be ensured between the two stop band filters.
  • the diplexer of FIG. 7 was simulated and the transmission response of the two filters is provided by the curves on top of FIG. 7 while the reflection response of the two filters is provided by the curves at the bottom of FIG. 7 . It can be seen that a low band rejection is thus obtained at around 5.15 GHz and a high band rejection in the range 5.5-5.7 GHz is obtained with a level of rejection comprised between ⁇ 30 and ⁇ 40 dB. It is noted that the bandwidth of the rejected band in low band is narrower than in the high band. This phenomenon is linked to the structural differences of the resonators, namely in the same direction or head to tail, inducing different couplings.
  • the second graph describes the adaptation in the bandwidth of rejection filters, in the order of 10 dB for the low band filter and greater than 15 dB for the high band filter.
  • the nickel-gold type surface treatment was left out. Stop band filters such as described in FIGS. 4 and 5 were produced on this substrate as well as a diplexer as described in FIG. 7 . The measurements of transmission and reflection were thus realised with these different circuits and the measurement results are shown in FIG. 8 in part (a) for the filters and in part (b) for the diplexer.
  • FIG. 8 a describes for each band-stop filter, the comparative results obtained by measurement and by electromagnetic simulation, FIG. 8 b describes the reflection and transmission responses of 2 channels of the diplexer.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
US13/529,627 2011-06-29 2012-06-21 High rejection band-stop filter and diplexer using such filters Abandoned US20130002373A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1155819 2011-06-29
FR1155819A FR2977382A1 (fr) 2011-06-29 2011-06-29 Filtre stop bande a rejection elevee et duplexeur utilisant de tels filtres

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US20130002373A1 true US20130002373A1 (en) 2013-01-03

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US (1) US20130002373A1 (ja)
EP (1) EP2541674B1 (ja)
JP (1) JP2013021688A (ja)
KR (1) KR20130002967A (ja)
CN (1) CN102856613A (ja)
FR (1) FR2977382A1 (ja)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9252470B2 (en) 2013-09-17 2016-02-02 National Instruments Corporation Ultra-broadband diplexer using waveguide and planar transmission lines
US9288844B1 (en) * 2014-09-17 2016-03-15 Fortinet, Inc. Wireless radio access point configuration
US9565566B1 (en) 2015-08-21 2017-02-07 Qualcomm Incorporated 5 GHz sub-band operations
US9673499B2 (en) * 2015-08-28 2017-06-06 King Abdulaziz City For Science And Technology Notch filter with arrow-shaped embedded open-circuited stub
US10292260B2 (en) 2014-01-07 2019-05-14 Mitsubishi Gas Chemical Company, Inc. Insulating layer for printed circuit board and printed circuit board

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3008238A1 (fr) * 2013-07-04 2015-01-09 Thomson Licensing Filtre rejecteur de bande
CN103633400B (zh) * 2013-11-19 2016-04-13 华南理工大学 一种基于电磁混合耦合的微带双工器
RU2591299C1 (ru) * 2015-04-02 2016-07-20 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Новосибирский государственный технический университет" Фильтр гармоник
KR101675964B1 (ko) 2016-01-27 2016-11-15 연세대학교 산학협력단 피드포워드 구조를 이용한 높은 리젝션의 n-패스 대역통과 필터
CN108594641B (zh) * 2018-04-10 2021-05-28 天津大学 基于中心频率不对称的陷波滤波器抑制伺服谐振的方法

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US4731596A (en) * 1985-02-27 1988-03-15 Alcatel Thomson Faisceaux Hertziens Band-pass filter for hyperfrequencies
US4873501A (en) * 1986-06-27 1989-10-10 The United States Of America As Represented By The Secretary Of The Navy Internal transmission line filter element
US5015976A (en) * 1988-11-11 1991-05-14 Matsushita Electric Industrial Co., Ltd. Microwave filter
US20120087284A1 (en) * 2010-10-08 2012-04-12 Andrew Llc Antenna Having Active And Passive Feed Networks

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JPH10215102A (ja) * 1997-01-30 1998-08-11 Nec Corp マイクロストリップ帯域阻止フィルタ
CN1414658A (zh) * 2002-12-20 2003-04-30 清华大学 折叠形微带线谐振器及其滤波器
CN2702455Y (zh) * 2003-11-24 2005-05-25 海泰超导通讯科技（天津）有限公司 对称双螺旋结构谐振器及其滤波器
JP4489113B2 (ja) * 2007-11-26 2010-06-23 株式会社東芝 共振器およびフィルタ
CN101728621A (zh) * 2008-10-29 2010-06-09 海泰超导通讯科技（天津）有限公司 梳状结构微带谐振器及其滤波器
JP5240793B2 (ja) * 2009-03-09 2013-07-17 日本電波工業株式会社 デュプレクサ
EP2454781A4 (en) * 2009-07-14 2013-01-16 Saab Ab MICROWAVE FILTER

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4731596A (en) * 1985-02-27 1988-03-15 Alcatel Thomson Faisceaux Hertziens Band-pass filter for hyperfrequencies
US4873501A (en) * 1986-06-27 1989-10-10 The United States Of America As Represented By The Secretary Of The Navy Internal transmission line filter element
US5015976A (en) * 1988-11-11 1991-05-14 Matsushita Electric Industrial Co., Ltd. Microwave filter
US20120087284A1 (en) * 2010-10-08 2012-04-12 Andrew Llc Antenna Having Active And Passive Feed Networks

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9252470B2 (en) 2013-09-17 2016-02-02 National Instruments Corporation Ultra-broadband diplexer using waveguide and planar transmission lines
US10292260B2 (en) 2014-01-07 2019-05-14 Mitsubishi Gas Chemical Company, Inc. Insulating layer for printed circuit board and printed circuit board
US9288844B1 (en) * 2014-09-17 2016-03-15 Fortinet, Inc. Wireless radio access point configuration
US10015791B2 (en) 2014-09-17 2018-07-03 Fortinet, Inc. Wireless radio access point configuration
US9565566B1 (en) 2015-08-21 2017-02-07 Qualcomm Incorporated 5 GHz sub-band operations
US9673499B2 (en) * 2015-08-28 2017-06-06 King Abdulaziz City For Science And Technology Notch filter with arrow-shaped embedded open-circuited stub

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EP2541674B1 (en) 2014-10-01
FR2977382A1 (fr) 2013-01-04
CN102856613A (zh) 2013-01-02
KR20130002967A (ko) 2013-01-08
EP2541674A1 (en) 2013-01-02
JP2013021688A (ja) 2013-01-31

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